It Just Works™
By default, the Firefox driver creates a new Firefox profile for each test run, which is the recommended action.
You can specify an existing profile to use, such as your ‘default’ profile:
You can also create a new Firefox profile each test run using any of the options that you can configure in the about:config pane of Firefox
Native Events on Microsoft Windows
Native events are enabled on Windows by default and intend to provide a lower level interaction between webdriver and the operating system. However, these seem to cause problems in certain conditions. These can be easily disabled by setting the option on the Firefox profile:
Using Firebug with Watir-WebDriver
First download the Firebug xpi file, then use the following code: